QET-SOL: Negative-CI Solid Fuel Certificates Designed for Offset Pairing

For corporate emitters with hard-to-abate Scope 1 exposure from natural gas, LNG, or hydrogen combustion; for waste-to-fuel facility operators producing solid fuel from MSW-organic, paper, food waste, or yard waste feedstocks; for sustainability and ESG teams structuring offset budgets using negative-CI thermal instruments; and for corporate procurement programs pairing positive-CI QETs with negative-CI QET-SOL to net out Scope 1 fossil-CO₂ and Scope 3 upstream-fuel emissions, QET-SOL is unlike any other certificate in the QET family. Each token represents 1 MMBtu of solid fuel thermal energy with verified negative carbon intensity in kgCO₂e/MMBtu — produced through landfill-diversion avoided-emissions accounting under the QET-SOL methodology v1.2, anchored to ISO 14064-3 reasonable-assurance verification on the EarnDLT registry. This page is the buyer's view: what QET-SOL is, how the offset-pairing logic works, and why this is structurally different from a thermal coal certificate.

QET-SOL, in one paragraph. QET-SOL is Greentruth's negative carbon intensity solid fuel thermal token — each certificate represents 1 MMBtu of solid fuel thermal energy with verified negative CI in kgCO₂e/MMBtu (the methodology's Burcell GREET reference case produces −116.39 kgCO₂e/MMBtu). Designed for offset pairing: corporate buyers retire positive-CI QETs (QET-NG for natural gas combustion, QET-LNG, QET-Hydrogen) AND retire QET-SOL against the residual Scope 1 fossil-CO₂ and Scope 3 upstream-fuel exposure. Feedstocks are waste streams diverted from landfill — MSW-organic, paper/cardboard, food waste, yard waste — with avoided landfill emissions credit calculated using GREET 2023 waste factors. Cradle-to-gate scope, ISO 14064-3 reasonable assurance, materiality thresholds of 5% per batch and 2% per portfolio, uncertainty quantification at ≤10% of mean CI.

For the QET-NG positive-CI pairing partner

For the broader net-zero pathway framing

The product exists for a procurement problem that has, until recently, lacked a clean instrument: how does a corporate buyer with material Scope 1 emissions from natural gas, LNG, or hydrogen combustion — and a parallel Scope 3 Category 3 exposure on those purchased fuels — close the residual fossil-CO₂ exposure that operational abatement cannot eliminate in time for the next reporting cycle? The standard answers (high-integrity CDR for residual neutralization at long-term target year; voluntary offsets at lower integrity tiers) don't fit the interim problem cleanly. Neither does an instrument that simply substitutes a lower-CI version of the same fuel.

The certificate fills that gap with a structurally different instrument. Three properties define the product for a buyer:

• One MMBtu of solid fuel thermal energy, with verified negative CI. Where most environmental-attribute certificates carry a positive CI (the carbon intensity of producing the underlying energy), the token carries a verified negative CI through landfill-diversion avoided-emissions accounting. The methodology's reference case produces −116.39 kgCO₂e/MMBtu. The negative CI is not a marketing claim — it is the verified lifecycle calculation under GREET 2023 waste factors, anchored to an ISO 14064-3 reasonable-assurance opinion on the on-chain mint.
• Designed for offset pairing, not standalone consumption. The product is structured around the use case of pairing with positive-CI QETs (QET-NG, QET-LNG, QET-Hydrogen) at retirement. A buyer retires QET-NG to substantiate the Scope 3 Category 3 disclosure on purchased natural gas (replacing default upstream factors with verified producer-level CI), AND retires QET-SOL to net the residual Scope 1 fossil-CO₂ from combustion of that gas. The two retirements close the loop in ways neither retirement alone can.
• Procurement-ready as a registry-grade EAC. Acquisition, transfer, and retirement run through the same EarnDLT registry every other QET class does. The Marketplace surfaces QET-SOL in the unified cross-token inventory; the Machine-Ready API exposes the same lifecycle operations; the framework-aligned exports at retirement populate the same disclosure cycles.

For the foundational platform context

For the marketplace lifecycle context

This is the most important section on the page, because the offset-pairing use case is what makes QET-SOL operationally meaningful. The mechanics are clean once described.

A corporate buyer operates a natural-gas-fired industrial process or a hydrogen-fueled fleet. The combustion produces Scope 1 fossil-CO₂ emissions. The upstream methane footprint of the natural gas (or the embedded carbon in the hydrogen production) produces Scope 3 Category 3 exposure. The buyer's sustainability program has a near-term emissions target it cannot fully abate operationally inside the relevant reporting cycle.

The conventional procurement response addresses Scope 3 with primary-data substitution — replacing default upstream emission factors with a verified low-CI QET-NG retirement. That improves the Scope 3 line. It does not address the Scope 1 residual.

The negative-CI pairing extends the procurement workflow. The buyer retires the QET-NG to substantiate Scope 3 with primary-data quality (CI down from a default upstream factor to a verified producer-level number), AND retires the solid-fuel token against the residual Scope 1 fossil-CO₂ from combustion (the negative-CI thermal credit nets the positive-CI combustion emission, with the underlying integrity coming from the avoided-landfill-emissions calculation on the solid-fuel side).

The retirement record on each event preserves the pairing logic on-chain. The QET-NG retirement carries its claim identifier and the verified upstream CI; the negative-CI retirement carries its claim identifier and the thermal credit. An auditor opening either retirement record can trace the pairing back to the buyer's reporting cycle, the specific Scope 1 or Scope 3 line being addressed, and the underlying methodologies and verifier opinions.

This is structurally different from a voluntary carbon offset retirement, in two ways worth noting directly. First, the certificate is anchored in verified physical solid fuel production from waste-stream feedstocks — the negative CI is not a counterfactual project credit; it is the cradle-to-gate lifecycle calculation of an actual energy product produced from actual diverted-waste material. Second, the integrity discipline is ISO 14064-3 reasonable assurance at the same bar that anchors QET-NG, QET-RNG, and the rest of the QET family — not the voluntary-market offset assurance tier.

For sustainability programs that have been struggling to close interim Scope 1 residuals defensibly, this is the instrument the procurement architecture has been missing.

For biogenic CO₂ accounting treatment

For abatement-first net-zero framing

What is not eligible: virgin biomass not diverted from landfill, agricultural residues that would otherwise be returned to soil, fossil-derived solid fuels, and any feedstock whose alternative disposition is not landfill (and therefore does not produce an avoided-landfill-emissions credit). Thermal coal and analogous fossil solid fuels are explicitly outside the QET-SOL methodology scope.

The credit calculation is the integrity foundation of the negative-CI claim, and the methodology documents it in detail. The structure runs as:

Total Credit = Σ (Feedstock Mass × Avoidance Factor × Treatment Factor)

For each feedstock fraction in the production batch:

• Feedstock mass is measured in tons of the specific waste-stream fraction (paper/cardboard, food waste, yard waste, MSW-organic) diverted from the landfill-bound waste stream and into the solid-fuel production facility.
• The avoidance factor is the GREET 2023-derived emissions factor representing the methane and CO₂-equivalent emissions that would have occurred from anaerobic decomposition had the feedstock followed the counterfactual landfill pathway. Factors vary by feedstock type and reflect the methane-generation potential of the underlying material under typical landfill conditions.
• The treatment factor captures the efficiency of the alternative treatment pathway (capture, gas-collection systems, time-to-decomposition profiles) and is applied to produce the net avoided emissions credit.

The total avoided emissions credit is then applied to the net energy production from the solid fuel batch:

QET-SOL CI = (Total Process Emissions × Solid Fuel Allocation Factor − Avoided Emissions Credit) ÷ Net Solid Fuel Energy Production

Where total process emissions include electricity emissions, utility natural gas emissions, and fugitive emissions at the processing facility; the solid fuel allocation factor distributes process emissions between solid fuel and any co-produced biogas; and net solid fuel energy production is calculated from solid fuel mass × energy density × moisture correction factor.

In the methodology's Burcell GREET reference case, total process emissions are 3,997,000 kgCO₂e/yr (with solid-fuel allocation 0.996 producing allocated emissions of 3,981,000 kgCO₂e/yr), avoided emissions credit is 19,801,000 kgCO₂e/yr, and net solid fuel energy is 135,787.5 MMBtu/yr — producing a QET-SOL CI of −116.39 kgCO₂e/MMBtu.

The example illustrates the order of magnitude. The avoided-landfill-emissions credit dominates the calculation by a factor of roughly five over the process emissions, which is what produces the deeply negative CI characteristic of waste-diversion solid fuel production.

Argonne National Laboratory R&D GREET model

EPA WARM model for solid waste emissions

For the broader GREET methodology context

For corporate buyers retiring QET-SOL against Scope 1 offset-pairing claims — and the verifiers and auditors who eventually review those claims — the integrity of the negative-CI assertion depends on three structural properties operating together.

• ISO 14064-3 reasonable-assurance verification. Every mint requires an unmodified verification opinion under ISO 14064-3:2019 at reasonable-assurance level — the higher of the two assurance levels in the standard. The verifier must be accredited to ISO 14065:2020 by an acceptable accreditation body with sector-specific scope covering GREET LCA, waste-to-energy operations, and biogenic-emissions accounting. Materiality thresholds are 5% for individual certificate batches and 2% for aggregated portfolios per QET methodology Section 8.3. Limited assurance is not sufficient; reasonable assurance is the operative bar that the elevated tiers of the major frameworks expect.
• Single-mint enforcement at the registry layer. One MMBtu of verified solid fuel thermal energy produces exactly one token. The Hedera-anchored EarnDLT registry structurally rejects any attempt to issue a second token for the same MMBtu. This is the double-counting prevention discipline operating at the infrastructure level, not at the policy level — there is no operational pathway by which the same solid fuel production reaches active inventory across multiple registries simultaneously.
• Irrevocable on-chain retirement. When a buyer retires the certificate against an offset-pairing claim, the closing event is permanent. The Hedera state machine writes the token's status to RETIRED and rejects any subsequent attempt to un-retire, re-trade, or re-use it. The retirement record is queryable on the registry, immutable, and traceable back through every transfer to the original mint, the verifier's reasonable-assurance opinion, and the underlying feedstock-specific avoided-landfill-emissions calculation.

How ISO 14064-3 underpins the platform

How double counting is structurally prevented

Cradle-to-gate scope. The lifecycle scope is cradle-to-gate — feedstock sourcing, transport, preparation, solid fuel and co-product generation, on-site energy and process inputs, allocations, and avoided landfill emissions. End-use combustion emissions are excluded from the QET-SOL CI per QET methodology Section 4.4.2. This is the standard system-boundary convention for fuel-attribute certificates: the producer's responsibility ends at the gate; downstream combustion emissions remain on the buyer's Scope 1 inventory (where, of course, the offset-pairing logic with QET-SOL retirement applies).

The combined effect is that the negative-CI claim is mechanically defensible — the calculation methodology is documented, the uncertainty is disclosed, the allocation is explicit, and the scope boundary is consistent with the standard practice across the QET family.

EPA Greenhouse Gas Reporting Program

The architectural property worth holding: the offset-pairing program uses QET-SOL during the interim when operational abatement and direct substitution (RNG, electrification) cannot fully close the Scope 1 residual. As the abatement pathway matures and the residual shrinks toward the long-term target year, the procurement architecture migrates toward QET-CCS for the final residual-neutralization step. QET-SOL is the interim-period instrument; QET-CCS is the long-term-target-year instrument. The portfolio operates as a coherent procurement architecture across the full abatement-and-neutralization sequence.

For the abatement-first / neutralization-at-residuals framing

For mass-balance chain of custody

For the CDR / long-term residual context

A few important boundaries to surface directly — these matter because the negative-CI architecture is novel enough that buyers often arrive with incorrect mental models.

• It is not a thermal coal certificate. QET-SOL covers solid fuel produced from waste-stream feedstocks diverted from landfill, with avoided-landfill-emissions accounting producing the negative CI. Thermal coal — fossil-derived solid fuel with positive lifecycle CI — is explicitly outside the QET-SOL methodology scope. The two product categories share the word “solid fuel” and nothing else.
• It is not a voluntary carbon offset. QET-SOL is a registry-grade environmental-attribute certificate documenting verified production of solid fuel thermal energy with cradle-to-gate negative CI, anchored under ISO 14064-3 reasonable-assurance verification. The integrity discipline is the same that anchors QET-NG, QET-RNG, and the rest of the QET family — not the voluntary-market offset assurance tier.
• It is not a substitute for operational abatement. The offset-pairing use case is structured as an interim mechanism that closes Scope 1 residuals during the period when operational abatement (efficiency, electrification, fuel switching, RNG substitution) cannot fully eliminate the underlying emissions. As the abatement pathway matures, the QET-SOL pairing requirement shrinks. It is not positioned, sold, or documented as a permanent substitute for direct decarbonization.
• It is not interchangeable with QET-CCS. QET-CCS is the long-term-target-year residual-neutralization instrument anchored in geologic CO₂ storage; QET-SOL is the interim-period offset-pairing instrument anchored in waste-diversion avoided emissions. The two products serve different roles in the mitigation hierarchy and are not substitutes for each other.
• It is not a one-feedstock-equals-any-other-feedstock instrument. Feedstock type, regional sourcing, and the specific GREET 2023 avoidance and treatment factors applied are recorded on each token. A buyer's Discovery filter can target specific feedstock profiles; the retirement record carries the feedstock metadata into the buyer's disclosure cycle.